The invention relates to a thin-film resistor comprising a substrate which is provided with two connections which are electrically interconnected via a layer of a resistance material on the basis of a metal alloy having an intrinsically low TCR (temperature coefficent of resistance). The invention also relates to a sputtering target which can suitably be used to manufacture such a thin-film resistor.
Thin-film resistors based on metal alloys are known per se. These resistors include, more specifically, the so-called "precision resistors", which are resistors whose resistance value is accurately and readily reproducible. In general, the resistance material of this type of resistors is selected on the basis of binary and ternary metal alloys, such as CuNi, CrSi and NiCr(Al). These metal alloys are provided by means of sol-gel techniques, sputtering or vacuum evaporation. Dependent upon, inter alia, the exact composition and the thermal pre-treatment of these alloys, they exhibit a low TCR. The TCR of a resistor is to be understood to mean the relative change of the resistor as a function of temperature. The value of the TCR is customarily given in ppm/.degree.C. Metal alloys having an intrinsically low TCR are metal alloys which, when they are in thermodynamic equilibrium, exhibit a TCR whose absolute value is smaller than 100 ppm/.degree.C.
The known film resistors have several important drawbacks. For example, the composition of the binary or ternary metal alloy must be accurately selected in order to attain the intended, low TCR of the material. In the case of such an accurately selected composition, it is generally no longer possible to further adjust the sheet-resistance value and at the same time retain the low TCR value. In addition, the sheet resistance of said alloys proves to be relatively low. In the case of the above-mentioned alloys having a low TCR, the sheet resistance is of the order of 1 .OMEGA./.quadrature. (CuNi), 1 k.OMEGA./.quadrature. (CrSi) or 100 .OMEGA./.quadrature. (NiCrAl).